1. Field of the Invention
The present invention relates to a transducer temperature compensation circuit.
2. Discussion of Prior Art
Transducers whose sensitivity varies with temperature are widely used in industry. In general, it is necessary to provide some form of compensation for the temperature variation of the sensitivity. For instance, piezoresistive bridge transducers when used in vehicles are subjected to a very wide range of temperatures, and compensation for the variation of sensitivity with temperature is essential in order for such transducers to provide a useful indication of a measured parameter.
Piezo-resistive bridge transducers generally exhibit a sensitivity which is non-linearly dependent on temperature. It is known to provide a temperature compensation arrangement for such a transducer by means of a bridge power supply employing a thermistor network to control the bridge energising voltage, and hence transducer sensitivity, in accordance with temperature. The required slope of the temperature-dependence of the network is calculated from sensitivity measurements of the transducer. Although this technique provides compensation, it is difficult to achieve high accuracy without careful calibration.
Temperature compensation can be improved by trimming the compensation circuit at two or more temperatures so as to adjust the sensitivity of the transducer at these temperatures to required values. However, such techniques require repeated temperature cycling because the trimming procedures are not independent of each other i.e. trimming at one temperature affects the trim at another temperature.